1. The abdomen is deflated of all air by manual palpation of the abdomen and turning the trocar. The abdomen is re-inflated successively to 0.5, 1, 1.5, and 2 liters (IAV), and, at each volume, the intra-abdominal pressure (IAP) is measured while inflation is stopped. A maximum pressure of 15 mmHg is used. The lowest IAP or end expiration value is taken. This allows the drawing of the first APVR, the calculation of the E, PV0, and inflated volume at 15 mmHg.